Using Auto and Lambda to handle Signal?

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I have written this program that has a main function, inside which, I am creating two sockets, like this:

int sockfd1 = socket(AF_INET, SOCK_STREAM, 0);
int sockfd2 = socket(AF_INET, SOCK_STREAM, 0);

Now I do some stuff with them, and when the user presses Ctrl+C to terminate the process, I want to make sure the sockets close properly, so I do this:

auto sigTermHandler = [&] (int param) { close(sockfd1); close(sockfd2); };
signal(SIGTERM, sigTermHandler);

But this throws the following compilation error when compiled as g++ -std=gnu++0x <filename>.cpp:

error: cannot convert ‘main(int, char**)::<lambda(int)>’ to ‘__sighandler_t {aka void (*)(int)}’ for argument ‘2’ to ‘void (* signal(int, __sighandler_t))(int)’

Is it not possible to use lambda this way to handle signals? Please advise.

P.S. I know I could put that in a destructor, if I did proper OOP, but I am curious to see if this works.

signals c++11 posix lambda c++
3 Answers

A little late but if someone needs such a solution one can use std::function as a wrapper to hold a lambda capable of capturing variables:

#include <functional>
#include <iostream>

namespace {
std::function<void(int)> shutdown_handler;
void signal_handler(int signal) { shutdown_handler(signal); }
} // namespace

int main(int argc, char *argv[]) {
  std::signal(SIGINT, signal_handler);
  MyTCPServer server;
  shutdown_handler = [&](int signal) {
    std::cout << "Server shutdown...\n";
    server.shutdown();
  };
  server.do_work_for_ever();
}
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